Time division duplex (TDD), as one of two basic duplexing modes, attracts more and more attentions along with the increasing requirement of wideband radio communication on bandwidth. In a TDD system, uplink transmission and downlink transmission use the same frequency resources and transmit uplink/downlink signals on different time slots. Familiar TDD systems include: time division-synchronous code division multiple access (TD-SCDMA) system in 3rd generation (3G) mobile communication technique and time division-long term evolved (TD-LTE) system in 4th generation (4G) mobile communication technique. Configuration of uplink slots and downlink slots is static or semi-static. Usually, uplink-downlink slot ratio is determined according to a cell type and an approximate service proportion during network deployment and remains unchanged. This is a simple and effective solution in a macro cell with a large coverage area. With the development of techniques, more and more pico cells and low-power base stations such as home NodeB are deployed for providing small coverage in a local area. In this kind of cell, there are less users and service requirements of the users change frequently. Therefore, the uplink-downlink service proportion in such cells needs to be changed dynamically. Although standard such as TD-LTE also supports dynamic online-changing of the uplink-downlink slot ratio of a cell, a complicated signaling procedure and much configuration time are required, which decreases system performance and cannot catch up with service change in real time.
Based on the above problem, an existing technique provides a dynamic uplink-downlink subframe allocation solution. The detailed processing is as follows.
During a certain time period, four kinds of subframe types are configured, including a subframe always as downlink transmission, a subframe always as uplink transmission, and subframes which act as uplink or downlink transmission flexibly. FIG. 1 is a schematic diagram illustrating a dynamic uplink-downlink subframe allocation solution according to the existing technique. In this technique, the adopted time period is a radio frame (which is an example, other time periods may be adopted), wherein                subframes #0 and #5 are always as downlink subframes, subframes #2 and #7 are always as uplink subframes, subframes #1 and #6 are special subframes (or may be seen as always downlink subframes), subframes #3, #4, #8 and #9 are configured as uplink or downlink transmission flexibly.        
For the last kind of subframe, the base station may configure flexibly according to a current service requirement and channel condition, so as to be fit for the dynamic change of the service requirement.
For the TDD system, downlink hybrid automatic repeat request (HARQ) feedback utilizes bundling and multiplexing techniques, i.e., acknowledgement (ACK)/negative acknowledgement (NACK) of multiple downlink subframes are fed back on a physical uplink control channel (PUCCH) of one uplink subframe.
For the multiplexing technique, ACK/NACK status is related to both information bit fed back on the PUCCH and an ACK/NACK/scheduling request (SR) resource index.
For the bundling technique, the ACK/NACK status is merely related to the information bit fed back on the PUCCH. However, in order to avoid ACK/NACK/SR resource conflict between users, a mapping method similar to that of the multiplexing technique is adopted for the ACK/NACK/SR resource index. Generally, one uplink-downlink configuration corresponds to one HARQ time sequence solution and one ACK/NACK/SR resource mapping solution. Therefore, there is no ACK/NACK/SR resource conflict.